.\"	$OpenBSD: apm.4,v 1.31 2014/01/21 03:15:46 schwarze Exp $
.\"
.\"	Copyright (c) 1998 Marco S. Hyman
.\"
.\"	Permission to copy all or part of this material for any purpose is
.\"	granted provided that the above copyright notice and this paragraph
.\"	are duplicated in all copies.  THIS SOFTWARE IS PROVIDED ``AS IS''
.\"	AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
.\"	LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
.\"	FOR A PARTICULAR PURPOSE.
.\"
.Dd $Mdocdate: January 21 2014 $
.Dt APM 4 i386
.Os
.Sh NAME
.Nm apm
.Nd advanced power management device interface
.Sh SYNOPSIS
.Cd "apm0 at bios0 flags 0x0000"
.Sh DESCRIPTION
The
.Nm
driver provides an interface to the Advanced Power Management
.Pq APM
BIOS functions.
The driver supports versions 1.0, 1.1, and 1.2 interface specifications.
.Pp
This driver also provides an interface to
.Xr acpi 4
on some machines.
.Pp
The low two bytes of the flags specify the version of the specification
driver should conform to in binary decimal notation.
The value of 0x0101 would specify version 1.1 of the interface
specification to be used.
.Pp
The value of 0x10000 specifies whether to leave interrupts enabled
when calling APM BIOS routines.
This is needed for some
.Tn IBM
laptops, the symptoms are
hangs and freezes on suspend, stand by, and hibernation activities.
.Pp
The value of 0x20000 specifies to swap the bytes of the battery
life estimation (the DX register) as given from the APM BIOS.
This is needed for some
.Tn SONY VAIO
laptops, such as some 505 models.
.Pp
Configuration options:
.Pp
.Bl -tag -width DIAGNOSTIC -compact -offset indent
.It Dv APMDEBUG
Enable various driver status messages.
.It Dv DIAGNOSTIC
Enable debugging messages.
.It Dv DEBUG
Enable other debugging messages.
.El
.Pp
The
.Nm
driver implements the following
.Xr ioctl 2
calls.
They are defined in
.In machine/apmvar.h .
.Bl -tag -width Ds
.It Dv APM_IOC_REJECT
.Em Not implemented . DO NOT USE .
.It Dv APM_IOC_STANDBY
.Pq Li "no parameters"
Request
.Dq standby
mode.
.It Dv APM_IOC_SUSPEND
.Pq Li "no parameters"
Request
.Dq suspend
mode.
.It Dv APM_IOC_GETPOWER
.Pq Li "struct apm_power_info"
Request the current power state.
The argument structure is as follows:
.Bd -literal -offset indent
struct apm_power_info {
	u_char battery_state;
	u_char ac_state;
	u_char battery_life;
	u_char spare1;
	u_int minutes_left;
	u_int spare2[6];
};
.Ed
.Pp
The following values are defined for
.Va battery_state :
.Bl -tag -width Ds
.It Dv APM_BATT_HIGH
Battery has a high state of charge.
.It Dv APM_BATT_LOW
Battery has a low state of charge.
.It Dv APM_BATT_CRITICAL
Battery has a critical state of charge.
.It Dv APM_BATT_CHARGING
Battery is not high, low, or critical and is currently charging.
.It Dv APM_BATT_UNKNOWN
Can not read the current battery state.
.It Dv APM_BATTERY_ABSENT
No battery installed.
.El
.Pp
The following values are defined for
.Va ac_state :
.Bl -tag -width Ds
.It Dv APM_AC_OFF
External power not detected.
.It Dv APM_AC_ON
External power detected.
.It Dv APM_AC_BACKUP
Backup power in use.
.It Dv APM_AC_UNKNOWN
External power state unknown.
.El
.Pp
The
.Va battery_life
value contains the estimated percentage of battery life available.
100% indicates a full charge.
.Pp
The
.Va minutes_left
value contains the estimated number of minutes of battery life
remaining.
.It Dv APM_IOC_NEXTEVENT
.Pq Li "struct apm_event_info"
The APM driver stores up to
.Dv APM_NEVENTS
events.
This was defined as 16 at the time this documentation was written.
If the event list is full when a new event is detected the new event is lost.
.Dv APM_IOC_NEXTEVENT
ioctl returns the next event on the list or
.Er EAGAIN
if the event list is empty.
The format of the returned event is:
.Bd -literal -offset indent
struct apm_event_info {
	u_int type;
	u_int index;
	u_int spare[8];
};
.Ed
where
.Va index
is a sequential count of events that can be used to check if any
events were lost and
.Va type
is one of:
.Bl -tag -width Ds -offset indent -compact
.It Dv APM_STANDBY_REQ
.It Dv APM_SUSPEND_REQ
.It Dv APM_NORMAL_RESUME
.It Dv APM_CRIT_RESUME
.It Dv APM_BATTERY_LOW
.It Dv APM_POWER_CHANGE
.It Dv APM_UPDATE_TIME
.It Dv APM_CRIT_SUSPEND_REQ
.It Dv APM_USER_STANDBY_REQ
.It Dv APM_USER_SUSPEND_REQ
.It Dv APM_SYS_STANDBY_RESUME
.El
.It Dv APM_IOC_DEV_CTL
.Pq Li "struct apm_ctl"
Allows an application to directly set the
APM operating mode.
The argument structure is as follows:
.Bd -literal -offset indent
struct apm_ctl {
	u_int dev;
	u_int mode;
};
.Ed
.Pp
.Va dev
indicates the device, typically
.Dv APM_DEV_ALLDEVS .
.Pp
.Va mode
indicates the desired operating mode.
Possible values are
.Bl -tag -width Ds -compact -offset indent
.It Dv APM_SYS_READY
.It Dv APM_SYS_STANDBY
.It Dv APM_SYS_SUSPEND
.It Dv APM_SYS_OFF
.It Dv APM_LASTREQ_INPROG
.It Dv APM_LASTREQ_REJECTED
.El
.It Dv APM_IOC_PRN_CTL
.Pq Li "int"
This
.Xr ioctl 2
controls message output by the APM
driver when a power change event is detected.
The integer parameter is one of:
.Bl -tag -width Ds
.It Dv APM_PRINT_ON
All power change events result in a message.
This is the normal operating mode for the driver.
.It Dv APM_PRINT_OFF
Power change event messages are suppressed.
.It Dv APM_PRINT_PCT
Power change event messages are suppressed unless the estimated
battery life percentage changes.
.El
.Pp
However, in no case will power status messages be displayed until the
battery life goes below the percentage in the
.Xr sysctl 8
state variable
.Dv machdep.apmwarn .
Setting
.Dv machdep.apmwarn
to zero disables all warnings regardless of the
.Dv APM_IOC_PRN_CTL
setting.
.El
.Pp
As noted above, the operation of the APM
driver can be modified using the
.Dv machdep.apmwarn
.Xr sysctl 8
variable.
Another driver modifier is the
.Dv machdep.apmhalt
variable.
When
.Dv machdep.apmhalt
is set to 1 the APM
power down code is modified in a way necessary for correct operation on
some systems, mainly
.Tn IBM
laptops.
If your system does not power down when given the command
.Li "halt -p"
try setting
.Dv machdep.apmhalt
to 1 using
.Xr sysctl 8 .
The variable can be set at boot time in
.Xr sysctl.conf 5 .
.Sh FILES
.Bl -tag -width "/dev/apmctlXXX"
.It /dev/apm
Power management data device.
May only be opened read-only.
May be opened by multiple concurrent users.
.It /dev/apmctl
Power management control device.
May be opened read-write or write-only.
May only be opened by one user at a time.
An attempt to open the file when in use will fail, returning
.Er EBUSY .
.El
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr intro 4 ,
.Xr sysctl.conf 5 ,
.Xr apm 8 ,
.Xr apmd 8 ,
.Xr halt 8 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver source code contains these copyrights:
.Pp
.Bl -item -compact
.It
.Li Copyright (c) 1995 John T. Kohl.  All rights reserved.
.It
.Li Copyright (C) 1994 by HOSOKAWA Tatsumi <hosokawa@mt.cs.keio.ac.jp>
.El
.Pp
\&...and has been hacked on by many others since.
.Sh BUGS
Not all the BIOSes support power down the way we are attempting
to execute it.
.Pp
Not all BIOS vendors even read the specification.
